Processing of products, typically meat products such as by smoking, cooking, chilling, or the like is commonly carried out by passing such products along a conveyor system through one or more sequential chambers, to achieve the various processing steps, or to progressively achieve the different stages in the desired processing. Different products will require to be processed at different conditions within each chamber or within each stage of the continuous chamber. Products of this type requiring different processing conditions have, of course, of necessity been processed in different batches at different times. The appropriate conditions must be established in each stage of the processing line or chamber as are needed for such products.
Accordingly, it is the general practice to provide such processing lines which are capable of accepting a single type of product at a time. Naturally the quantity of the particular type of product being processed may vary widely, but so long as that one type of product is being processed, no other product requiring different conditions or timing could be passed through the processing facility.
This had the effect of somewhat restricting the flexibility of production. It meant that the processing facilities would have to be operated at conditions which matched either the product for which there was currently the most demand, or alternatively, the product for which the raw materials were currently most readily available or most suitable.
Other types of products would have to be delayed while the one product was being passed through the processing line.
Generally speaking, if it was desired to process more than one type of product simultaneously, then it was considered necessary to erect two separate processing facilities. This of course simply doubled the cost of the initial investment. This increase in investment was not always warranted by market conditions or availability of product and consequently it was not always possible to justify the doubling of the capital investment to achieve the desired flexibility.
An additional disadvantage of the provision of the former type of processing facility was the factor of the physical area, or real estate occupied by the facility Generally speaking, in order to be operated satisfactorily, the processing chamber was in the form of an elongated oven, which may either be considered as a single continuous chamber, or which may be considered as a series of sequential chambers joined together. A continuous conveyor system such as an overhead conveyor rail ran throughout the chamber, and batches of product were loaded onto the rail at spaced intervals, and moved at a fixed speed.
In the meat processing industry in particular, the products are loaded on product hangers by hand, and the product hangers are then transferred onto the conveyor rails also by manual labour. As a result, there were certain physical limitations on the size of the product hanger and the amount of product that could be hung on any one hanger. This in turn imposed certain dimensional limitations on the interior size of the chamber. Thus the chamber could have no greater width and height dimension than was required to accept the passage of a single manual load of such product. Some attempts to increase the size of the chamber have been proposed such as in U.S. Pat. No. 1,581,519, but have not found wide acceptance.
The result of these various limitations was therefore that in order to achieve a satisfactory processing capacity to meet large scale demands, the processing chambers themselves became of very considerable length. Since the processing chambers were located all on a common level, the end result was that the processing chamber occupied a very considerable amount of space which added considerably to the overall capital cost of the installation. An additional factor in the design and disadvantages of the commonly accepted form of processing facility was that in such processing chambers it is required to provide a highly efficient form of air circulation, so as to achieve overall uniform conditions at each stage throughout the chamber. This was essential in order to provide uniform product appearance and condition, after passage through the processing stages.
It was also necessary that such conditions should be capable of being controlled very narrowly, to close tolerances.
In order to achieve this, in the usual elongated processing chambers, they are provided with a relatively complex system of ducts, circulating fans, and temperature and humidity sensors, and temperature and humidity regulators and the like.
The provision of all these facilities along the full length of a very considerably elongated tunnel-like structure presents considerable engineering problems, and requires the inclusion of a large number of sensors and controls in order to maintain uniformity at the various stages.
Clearly, considerable economies can be achieved by making the interior dimensions of the chambers or ovens larger, and processing the meat products through the larger chambers in larger batches. At the same time, the speed of movement of the conveyor through such chamber would be reduced so that the end result would achieve essentially the same dwell time in the desired processing conditions at each stage throughout the chamber.
It will of course still be necessary to provide for highly efficient air circulation throughout the entire interior area of each of the zones, but provided suitable attention is paid to this aspect of the design construction, this can now be achieved. For example, there is disclosed in U.S. Pat. No. 4,250,917 and 4,310,020, and also in pending U.S. patent application Ser. No. 188,167, all of which have been assigned to the applicant of this application, various inventive aspects in the design of a batch processing chamber for processing meat products in batches. A highly efficient form of air circulation is achieved, which may be effected either from one side to the other, or from the sides to the center of the chamber or from the center to the sides, in a sequentially reversing manner, thereby providing for effectively uniform processing conditions throughout the entire cross-sectional area of a large chamber, resulting in the uniform processing of very large volumes of product.
In these batch chambers, a cage-like frame carrying a large volume of product is moved into the chamber, and the product is processed while standing still in the chamber.
By the application of these inventions uniform processing conditions can be maintained throughout the full extent of the cross section of the chamber while very large volumes of product are processed.
The supporting of such large batches of product may be achieved in various ways. For example, product such as weiners may be supported on meat product supports such as are shown in U.S. Pat. Nos. 3,594,858, 3,732,971, 3,792,508, and 3,982,300, all of which have been assigned to the applicant of this application. A skin of sausages from a sausage stuffing machine is loaded onto one of such hangers by hand. Such hangers can be used on a much larger form of support or "cage" in which a larger number, for example, four, six, eight or more such hangers each loaded with weiners may be suspended, and the cage when loaded may then simply be moved into the chamber, for example, on a fork-lift truck.
However, such a facility will only provide for the processing of a single type of meat product at any one time.
As stated, this is found to be unduly restrictive on the flexibility of manufacture.
Various different forms of meat products such as polish sausage and bologna, may be processed in conditions which are virtually identical to the processing of, for example, weiners, but will require to be handled and suspended in different ways from that used in connection with weiners.
Other meat products such as ham and other meats may be processed in different ways for different markets, for example some by smoking, others by cooking, and others by both smoking and cooking.
The processing times or dwell times, as they are known, in the processing chambers will vary depending upon the type of product, notwithstanding that the actual processing conditions, i.e. temperature, humidity and the like are identical. However, when using the usual type of batch chamber it is not normally possible to process such different types of meat products in the same chamber under the same conditions, and provide for different processing times.
For all of these reasons therefore, it is clearly desirable to provide for a continuous processing facility which offers solutions to all of these problems. In particular, such a facility should provide:
1. Capability of simultaneously processing more than one type of product under the same processing conditions, but for different dwell times.
2. A more economical use of space, brought about by a reduction in the length of the facility, and an increase in the interior cross-sectional dimensions, as compared with known continuous processing systems.
3. An improvement in the equipment for circulating air, and maintaining processing conditions, without increasing the complexity or cost of the equipment, and preferably reducing such costs.
4. Capability of supporting different, but compatible, products, in different batches, in the same chamber or zone.
5. Capability of moving loads of product along separate conveyor paths, at different rates, and in a step-wise manner, so that different dwell times can be established in different zones of the chamber, for different loads.